Hi Dee, 1For a sample solution is use nathelper module with rtpproxy. Use force_rtp to chang SDP information is INVITE/183/200OK SIP packet to transfer to rtpproxy server. It use this solution 2 Use STUN server. If you clients support STUN protocol, imploy a STUN server on external networks. Those clients on internal first use STUN protocol to get NAT information and use external IP address/port to communicate. 3 If you clients support RTP follow, it works like this: a. first RTP packet: internal client-------------------NAT--------------------> external client b. external client get NAT address/port by get the RTP packet source address/port c. external client change target address/port by the source address/port of first RTP packet d. internal client<-----------------NAT---------------------- external client e. two way RTP works Br, Wangji -----原始邮件----- 发件人: serusers-bounces(a)iptel.org [mailto:serusers-bounces@iptel.org]代表 Dee Lowndes 发送时间: 2004年2月21日 5:30 收件人: serusers(a)iptel.org 主题: [Serusers] SIP iptables question I have finally worked out the problem to an iptables issue and was wondering if anyone had some rules to sort this out. If two clients are on an external IP it works, if two clients are on an internal IP it works but if one client is internal and the other is external then the external guy can hear the internal but the internal guy hears nowt. Any idea/modules/rules to get around this? Thanks in advance, Dee _______________________________________________ Serusers mailing list Serusers(a)iptel.org http://mail.iptel.org/mailman/listinfo/serusers